Tuesday, 18 December 2012

Something Nasty For Creationists

Norovirus
Here's a nice (or rather nasty) example of evolution. You probably know someone who has been involved with it recently. If not, the chances are you will soon. It's a nasty little example of a seemingly pointless parasite which, if there was an intelligent designer, would be evidence of its malignant intent. Not even the defence of callous indifference can be offered. It does nothing but make us feel unwell and inconvenience us in rather alarming and embarrassing ways, striking often with little prior warning.

The virus, which is highly contagious, causes vomiting and diarrhoea. As there is no specific cure, you have to let it run its course, but it should not last more than a couple of days. If you get norovirus, make sure you drink plenty of fluids to avoid dehydration and practise good hygiene to help prevent it from spreading.

I'm talking about norovirus, also called the winter vomiting virus because it tends to be prevalent in winter. The name 'norovirus' is derived from Norwalk virus. It is thought to be responsible for 50% of foodborne gastroenteritis in the USA. Between 600,000 and 1 million people in the UK catch norovirus every year.

Symptoms especially include forceful vomiting and watery diarrhoea. They may also include general malaise, headache, raised temperature and aching limbs. Although unpleasant, most people recover completely within two or three days. Hospitalisation is rarely necessary and deaths are very rare.
Noroviruses are a genetically diverse group of single-stranded RNA, non enveloped viruses in the Caliciviridae family. The viruses are transmitted by fecally contaminated food or water, by person-to-person contact, via aerosolization of the virus and subsequent contamination of surfaces.
Norovirus 'Family Tree'
Normally, humans and other animals become resistant to infections, especially to viral infections, by making anti-bodies which attack and destroy subsequent infections before they can gain hold. However, norovirus very rapidly mutates and changes so that anti-bodies formed against one strain are ineffective against other strains. The virus is able to evolve in response to changes in its environment (i.e your intestines). Because of this rapid evolution norovirus exists in a bewildering array of different genotypes and strains. The prevalent genotype in humans (GII) has some nineteen different strains alone.
Reports have shown a link between the expression of human histo-blood group antigens (HBGAs) and the susceptibility to norovirus infection. Studies have suggested the viral capsid of noroviruses may have evolved from selective pressure of human HBGAs.[1]
Studies have shown how the RNA from different strains and even different genotypes frequently recombine to produce new forms.
Histo-blood group ABO(H) antigens with a terminal fucose act as receptors for human norovirus in the gastrointestinal tract. A single nucleotide mutation (G428A) in the fucosyltransferase gene on chromosome 19 provides strong protection from infection in 20% of the white population,[2] although some norovirus genotypes can infect persons carrying this mutation.
There is no specific treatment for norovirus.

It's best to let the illness run its course and your body usually fights off the infection within a couple of days. You don't need to see a doctor.

It is important to have plenty to drink and, if you feel the need, paracetamol for any fever or aches and pains.

Try to eat foods that are easy to digest, such as soup, rice, pasta and bread. Babies should continue with their normal feeds.

To reduce the risk of passing the virus on to others, wash your hands regularly and stay at home until you are clear of symptoms for 48 hours.
So, there we have a superb example of two organisms in an evolutionary spiral: a parasitic virus and its host, in this case, us. The virus has evolved a strategy for... well... evolving quickly to overcome its host's defences, which places a huge selection pressure on the virus so it's adaptation has had to be profound. However, because the parasite doesn't cause much harm in terms of our ability to survive and reproduce, adaptation in us has been quite small. In fact, there is some indication that some otherwise harmless mutations in a protein in the human intestine makes the carriers slightly more susceptible to norovirus infection. But, twenty percent of some human populations have a mutation which gives them complete protection from most, though not all, strains.

So why only twenty percent? Why hasn't this beneficial, protective mutation spread throughout the human gene-pool the way beneficial genes are expected to do, according to Darwinian evolutionary theory? And why haven't the mutations making us more susceptible been eliminated?

Quite simply because a nasty bout of D&V for a day or two doesn't put any significant evolutionary selection pressure on us because it doesn't affect our ability to have and nurture children to any appreciable extent. To the virus though, its very survival depends on it. It uses us to spray itself around, literally.

But imagine what would happen if a chance mutation turned a strain of norovirus into a virulent killer. How would those twenty percent of immune people fare and what would the proportion of people carrying the protective mutation be once the lethal epidemic had blown its course? Who are going to be the ones to survive and produce the next generation of humans?

That folks, is evolution!

It really IS that simple, and we can see it in progress right now. Fortunately, it's the virus, or rather the RNA it's a carrier for, which is having to evolve like crazy to stay alive.

What is the norovirus for exactly? The norovirus exists simply because it exists. It has no purpose and no function other than producing noroviruses and so perpetuating a strand of RNA through time. Its prevalence throughout the world testifies to its outstanding success in that endeavour. It outnumbers the human population of earth probably by several orders of magnitude. If the norovirus could have a point of view it would see the universe, and its hosts, including us, as being there for its convenience with no function other than helping it to make more copies of its RNA.

If it were intelligent enough to think, though not intelligent to think well enough, and it believed in a creator god, it would undoubtedly believe its god created the world including us, for its benefit. If argued purely on numbers it could well be challenged in that belief by other viruses, bacteria, fungi and some other single-celled eukaryote organisms, and possibly some nematode worms, but no mammal, including man, would come anywhere close to these numbers.

In terms of intelligent design and especially intelligent design by a benevolent designer who created everything for the benefit of humans, noroviruses make no sense at all, unless the 'intelligent designer' enjoys seeing humans gushing noxious liquids from both ends and feeling rather dreadful for a few days.

Darwinian Evolution, on the other hand, positively predicts them, without resorting to magic and infinitely multiplying magic entities.


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